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Biological Psychology: Neurons & Synaptic Transmission

What is a Neuron

A neuron is a nerve cell that is electrically excitable and communicates with other cells via specialized connections called synapse. The neuron is the basic component of the nervous system and can transmit signals both electrically and chemically.

The 3 Types of Neurons:

  1. Sensory Neuron – Sensory Neurons carry messages from sensory receptors along the nerves within the PNS to the CNS.

  2. Motor Neurons – Carry messages from the CNS through the PNS to effectors in the body.

  3. Relay Neurons – Relay neurons connect sensory neuron and motor neuron as well as to other relay neuron.

What is Action Potential?

What is Synaptic Transmission?

Neural networks are groups of neurons that communicate with one another. It is important to note that they do not touch each other hence there is a tiny gap know as the synaptic cleft.

Signals within the neurons are transmitted electrically however signals between neurons are transmitted chemically across the synapse. Synaptic transmission refers to this chemical process of using neurotransmitters to transmit signals to other neurons.

When the action potential reaches the terminal button, neurotransmitters are released from the synaptic vesicles into the synaptic cleft to travel across and reach the receptors. As they cross, they synaptic cleft and reach the receptors at the postsynaptic neuron the neurotransmitters fit in like a key and lock. Any neurotransmitters left in the synapse are reabsorbed, this is known as reuptake and means the neurotransmitters can be used again.

What is Excitation and Inhibition?

Neurotransmitter can either be excitatory or inhibitory depending on the effect they have on nearby neurons. Neurotransmitters that increase the likelihood of causing the next neuron to fire are described as excitatory (such as dopamine) whilst neurotransmitters that decrease the likelihood of the next neuron firing is called inhibitory (such as serotonin).


Summation links with whether a neuron fires or not based on the adding (summation) of inhibitory and excitatory inputs. If the net effect is inhibitory, this decreases the likelihood of the neuron firing whilst an excitatory net effect increases the likelihood of depolarisation and, hence firing.


References/ Further Reading:

Neuron – Wikipedia -

Neurotransmitters – Wikipedia -

Synaptic Transmission – Wikipedia -

Summation – Wikipedia -

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